Duolingo's Tips and Notes for object pronouns:
Unfortunately nonbinary pronouns aren't really a widespread thing in Dutch. "Zij" is used, depending on conjugation, as a plural (like the plural they in English) or as the singular feminine (like she). Here are a few resources that could help: https://nonbinary.wiki/wiki/Gender_neutral_language_in_Dutch https://www.quora.com/What-pronouns-do-non-binary-people-use-in-Dutch https://www.reddit.com/r/learndutch/comments/grxzt9/nonbinary_pronoun/
In my experience, most people just switch to English. However, I wouldn't be surprised if new pronouns would start being used, like hen in Swedish.
I believe it goes like this:
Hij zag hen.
He saw them.
Hen is "directly" carrying the action of being seen.
Hij gaf hun de boeken.
He gave them the books.
De boeken is "directly" carrying the action of being given; hun is "indirectly" taking the action of the giving. Hun can, in many instances, be replaced by aan hen: Hij gaf aan hen de boeken.
It is my understanding that this hen/hun distinction is not universally followed in Dutch.